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Reviews > Hydration Systems > Bladders > Platypus Insulator Hydration System > Test Report by Kurt Papke

Platypus Insulator Hydration System

Test Series by Kurt Papke

Initial Report - November 28, 2008

Field Report - February 10, 2009

Long Term Report - April 10, 2009

Tester Information

Name: Kurt Papke
Age: 55
Gender: Male
Height: 6' 4" (193 cm)
Weight: 220 lbs (100 kg)
Email address: kwpapke at gmail dot com
City, State, Country: Minneapolis, Minnesota USA
Backpacking background: mostly in Minnesota - I have hiked all of the Superior Hiking Trail and Border Route.  My preferred/typical backpack trip is one week, mostly in the Spring/Fall seasons.  I do periodic day hiking in Michigan, Wisconsin, Utah, Colorado and Oregon.  I do a fair amount of Winter snowshoeing and cross-country skiing, so keeping hydrated in cold weather is important to me.

Initial Report - November 28, 2008

The Platypus Insulator is an insulated water reservoir and drinking tube designed to keep water cool in the hot sun, and more importantly for me, to keep water from freezing during outdoor Winter activities.  It is essentially an insulated Platypus Big Zip SL reservoir and drinking tube.

Product Information

Manufacturer: Cascade Designs, Inc.
Year of manufacture: 2008
Manufacturer website:

(Product label)
Big Zip SL Listed
Reservoir Capacity
100 oz
(3 l)
100 oz
(3.0 l)
100 oz
(3.0 l)
109 oz
(3.225 l)
8 x 21 in
(20 x 53 cm)
7.75 x 18.75 in
(19.5 x 47.5 cm)
7.5 x 17 in
(19 x 53 cm)
8.25 x 18.5 in
(21 x 47 cm)
5.4 oz
(152 g)
Not listed
4.5 oz
(135 g)
13.1 oz
(370 g)

Dimension discrepancy: the difference between the listed product label and measured length for the reservoir is substantial -- 2.5 in (64 mm)  In fact the dimensions from the website were closer to my measurements.  I thought perhaps the difference was that the manufacturer measured the reservoir with the top flap open, but that is 22 in (56 cm).  The only way I could come up with 21 in (53 cm) was to measure from the top of the stretched handle to the bottom of D-ring, with the latter extended downward.  I will stick with my measured length above, as that is the practical limit for fitting the insulated reservoir into a hydration sleeve.  There are some significant discrepancies between the listed dimensions on the product label and on their website, and the website has an entry labeled "Weight:", but it is missing a value.

The weight discrepancy between the label and measured value is even larger - a factor of approximately 2.5:1.  I added a column in the table for the listed specs for the Big Zip SL reservoir-only, this should be the specs for the Insulator reservoir and tube without the insulation.  The listed weight for the uninsulated reservoir is quite close to the listed weight of the Insulator, but still off by approximately 20%.

The manufacturer's specs for this product are a mess.

Product Description

Platy Insulator front viewCloseup of supply hose fittingThe picture to the left is the front view of the Insulator.  The three D-rings on the left, right and bottom are readily visible.  The insulated hose is coiled in a loop with the blue bite valve cap at left.  The only portion of the reservoir visible in the photo is the supply hose fitting just above the bottom D-ring.  A closeup of the fitting is shown at right.  Not visible beneath the label at the top is the insulation flap closure buckle.

The sleeve insulation appears to be foam with a silnylon cover.  The supply tube insulation seems to be neoprene, with no fabric cover.  The supply tube insulation is approximately 0.25 in (6.3 mm) thick, and the sleeve insulation slight less, though its thickness is difficult to measure with the fabric cover.

The statement of "BPA free" is readily legible on the label at the top of the photo.  There is a claim near the bottom of the label for the SlimeGuard anti-microbial used to preserve water taste which is not legible in the photo.  On the backside of the label are the product features and specifications.  No instructions were supplied with the unit.

The back of the unit looks similar, without the hose fitting of course.  The sleeve also has a webbing/rubber handle, allowing the Insulator to be comfortably carried.  On the bottom of the sleeve back is a small drain hole.

The reservoir can be removed from the Insulator by disconnecting the supply hose from the fitting, unbuckling and opening the flap, and lifting it out.  When I tried this, it slid out nicely.   The supply hose is disconnected by pressing on the gray button shown in the closeup on the right.  When I tried this, the button depressed with a moderate amount of effort, and the hose popped right off.  When the hose is disconnected a valve closes in the fitting preventing fluids from draining out of the reservoir.  This should make it easier to carry the reservoir to a body of water for filling without dragging the bite valve and supply tube on the ground.

Reservoir removed from sleeveReservoir openingThe reservoir is shown removed from the insulated sleeve and disconnected from the supply tube in the photo at left with a 12 inch (30 cm) ruler on the side for scale.  Visible on the right of the reservoir are the fill gradations, in 0.5 l (17 oz) increments.

On the top of the reservoir is the blue SlideLock closure and a white plastic carrying strap for the reservoir itself.  To the right of the SlideLock is a black elastic cord which attaches the removable SlideLock to the reservoir body.  It is good Platypus made this cord elastic -- every time I open the SlideLock I overshoot and the elastic cord is very forgiving.

The picture at right shows the reservoir with the SlideLock removed, and the top opened for filling or draining.  The top closure is similar to a ziplock-style bag, but more heavy-duty.  The blue SlideLock piece keeps the top from accidentally opening.  When I filled the reservoir to capacity, dried it off and held it upside down I could observe no leakage from the top closure.

Initial Impressions

Backpack Hydration Sleeve Compatibility

I use my hydration reservoirs in a variety of backpacks, and have experienced problems with reservoirs fitting properly.  I don't know whether to blame this on the backpack manufacturers or the hydration system manufacturers, but nonetheless it is an important issue for me.  One of the first things I did with the Insulator is attempt to fit it into the sleeve of three backpacks.

Insulator fits (barely) into REI Traverse daypackAt left is a photo of the Insulator installed in the hydration sleeve of my REI Traverse daypack.  This is my main pack for single-day trips.  It has a good-sized sleeve and dual supply tube ports.

The Insulator fits just exactly.  I was able to zip the top of the pack closed with no problems, though it was snug.  There was no need to hang the reservoir from the pack hooks due to the snug fit.

The supply tube is shown threaded through the port on the left side of the photo.  Surprisingly, the bite valve cap went through the port with no problems.
Insulator does not fit in Mountainsmith Boundary packAt right is a photo of my attempt to install the Insulator in my Mountainsmith Boundary backpack.  See my review of this pack on  Noted in my review is the fact that this pack has a hydration sleeve that is much too small for the tall Platypus reservoirs, and in fact the Insulator doesn't come close to fitting.  It sticks out over 6 in (14 cm).

I have used my 3 l (100 oz) Platy Hoser reservoir in this pack before, but it has no insulation, and I was able to fold it over to get it to fit reasonably.  I would not want to fold the Insulator and damage it, nor was it easy to fold when I tried it.

Insulator installed in Sierra Long Trail 90Sierra Long Trail hydration tube portOn the left is a photo of the Insulator installed in my Sierra Long Trail 90 backpack.  This pack, as noted in my test report on, has a capacious hydration sleeve and the Insulator fit with plenty of room to spare.

Visible in the top center is the handle of the Insulator hanging on the lone hydration reservoir hook in the Long Trail 90.  It seemed to stay on the hook, but time will tell if it stays there.

In the photo at right is the disconnected end of the supply tube getting ready to be fed through the hydration port on the Long Trail 90.  The insulated bite valve did not fit through the port, so I had to disconnect it and feed the fitting end through.  This worked just fine.  The supply tube insulation was snug in the port, but fed through with no problems.


Platypus claims the HyperFlow bite valve on the Big Zip "offers the highest flow rate on the market", though I was not find any data to substantiate this claim.  My first few sips from the reservoir suggest that indeed there is very little flow resistance from the valve.

As can be seen in some of the earlier photos in this report, the bite valve is covered by a molded plastic cap, the cover of which is held in place with a raised flange.  The cap pops off pretty easily at room temperature, but experience will tell if that ease is maintained at cold temperatures with gloves on.

The bite valve does not come with a clip, but the cover described in the preceding paragraph has a hole in it ostensibly for fastening to a shoulder strap.


I have tested one other hydration system with a supply tube fitting that is not totally dissimilar to the one on the Insulator.  The other one leaked badly even after replacing the gasket, and eventually I had to Superglue it shut.  The Insulator fitting benefits from having the supply tube insulation as a stress relief mechanism which should prevent too much force being applied to the fitting causing failure.  This is certainly something I'm going to be keeping my eye on in the next four months.

Pleasant Surprises

This seems like a very complete insulation system: the supply tube insulation seems really beefy, and the bite valve cap looks like it should be effective.  I look forward to testing their performance in the field.

This concludes my Initial Report on the Platypus Insulator Hydration System.

Field Report - February 10, 2009

One of the items I neglected to put into my Initial Report is the functionality in the Insulator for draining the supply tube in the field.  Despite the insulation, it is important at cold temperatures particularly at night, to drain the supply tube so it does not freeze solid.  The good news is the Insulator makes this simple: I just detach the tube from the reservoir and suck the water out of the system.  The valve on the connector prevents the water from draining from the tube when disconnected, but does not prevent water/air suction up the tube.  Using this feature in the field is not always simple, as disconnecting the supply tube from the reservoir when it is packed in my backpack requires removing most of the items in my main pack compartment to access the reservoir.  This constraint of course is true of any hydration reservoir with a removable supply tube, and not unique to the Insulator.

Taste Test

Just after filing my Initial Report I filled the Insulator reservoir with tap water, took a drink to make sure the supply tube was filled with water, and let the system sit with no activity for over two weeks.  When I took several drinks from the system at the conclusion of this two-week period I could detect no off-tastes.  Though it is unusual for me to leave water in a hydration system for extended periods, it's nice to know that it does not impart any flavor to the water that I could detect.

Field Locations/Conditions

December 8-10, 2008
January 11-13, 2009
Superior Hiking Trail along the Beaver Bay to Penn Creek section Superior Hiking Trail near Finland, Minnesota, from Egge Lake to Leskinen Creek
750 to 1250 ft (230 to 380 m) 1322 ft to 1726 ft (400 m to 525 m)
Low of -2 F (-19 C) to a high of 15 F (-9 C) Low of -27 F (-33 C) to a high of 15 F (-9 C)
Forested with rivers
Rolling hills with several steep ascents and descents
Forested with lakes and rivers
Rolling hills with no steep ascents


Bite valve attached with S-Biner
Since the Insulator does not come with standard hardware for attaching the bite valve to my pack shoulder strap, I used a Nite Ize #2 S-Biner as shown in the above photo.  The hole in the bite valve cover seemed like it would work great for this purpose.  The S-Biner allowed me to quickly and easily detach the bite valve from my shoulder strap and move it to my mouth.  On subsequent hikes I found that clipping the hose to the hole in the cap caused the cap to pop off, and I shifted to using the cap strap just above the cap hole shown in the above photo.  That worked well as the S-Biner has much less mechanical advantage at that attachment point, and the problems of the cap popping off disappeared.

I had read the FAQ on the Platypus website, and one of their recommendations for cold weather use is to blow any water in the supply tube back into the reservoir after drinking to minimize the probability of freezing.  I attempted to do this before hitting the trail on the December trip, but the reservoir was quite full and tightly packed in the hydration sleeve, so I was unable to develop enough mouth pressure to push the water back out of the supply tube.

My first drink from the Insulator on the December trip was approximately 90 minutes after getting out of the car.  The bite valve was completely frozen up already, and I was unable to thaw the valve/supply tube for the rest of the trip.  Despite being able to use the Insulator for hydration while in-motion, I continued to use the insulated reservoir for water carrying and storage.

On the January trip I was able to keep the supply tube from freezing up the entire first day by under filling the reservoir and blowing the water back into it at temperatures down to about 10 F (-12 C).  However, despite clearing the tube as best I could that night it froze up and I was once again constrained to using the Insulator as a water carrier for the rest of the trip.

Boiled Platypus for breakfastI was impressed with how well the insulated reservoir kept water in liquid form during cold nights.  On December night #1 I filled up the reservoir with warm water and stowed it in my pack out in the open.  The temperature dropped to 0 F (-18 C) that night, and the water in the reservoir did not freeze, at least not solid.  I was able to extract enough water for breakfast, and while heating my morning beverage the remaining water began to freeze, so I immersed the slushy end of the reservoir in hot water as shown in the photo at left.

On night #2 it was supposed to get even colder, and indeed the temperature dropped to -2 F (-19 C).  To prevent freezing, I hung the Insulator from the ridge line of my hammock and kept it inside the shelter.  This worked very well, and I had no problems with slushy water the next morning.

Filling the insulator from a potOne of the activities I found I had difficulty with was filling the reservoir from my kettle (shown in photo at right from the January trip), which I had to do since I was melting snow for water on both trips.  With its round bottom, it will not stand up on its own, so I had to use one hand to hold it up.  The SlideLock closure will also not remain open on its own, so it requires another hand (or at least some fingers) to prop it open.  My third hand (!) was used to pour the water from my kettle.  I tried using sticks and other items to prop it open, but nothing stayed in place very well.  Eventually I learned to hold the SlideLock open and hold up the reservoir by inserting two fingers or my thumb into the opening on one of the ends of the SlideLock.  This works, but if the water in the kettle is very hot and my aim is poor this can result in scalded fingers.

Another difficulty I had was opening the insulation flap clasp while wearing heavy gloves.  The clasp is quite small, and I found I had to remove my gloves to open the clasp and flap to remove the reservoir or for filling.  This was very uncomfortable in the cold.  I believe that gear that is intended for cold weather use should be designed to be used with gloves on at all times if possible.  This could be accomplished with the Insulator simply by using a larger clasp.

The glove configuration shown in the photo at right did allow me to open the clasp without removing anything.  On this January trip I used a stretch shell glove with wool gloves with no fingertips as a second layer for camp chores.

Day Hikes

After my problems on the first backpacking trip I decided to experiment more locally on some day hikes.

Walk: Wednesday December 17, Minnesota Landscape Arboretum in Chanhassen, hiked about 6 miles (10 km).  Altitude: 980 to 1100 ft (300 to 335 m).  Environment: 1 to 5 F (-17 to -15 C), light winds 0 to 7 mph (0 to 11 kph), sun was shining brightly.  The Insulator was carried in my REI Traverse pack as shown in the first photo above in the Backpack Hydration Sleeve Compatibility section.

On this walk I drank approximately every 25 minutes, and after drinking I blew the water back into the reservoir before putting the cap on.  When taking each drink, I noticed the bite valve was frozen but the small amount of ice thawed as soon as I bit down, and the supply tube never froze up.  I noticed I had to be careful not to bite down too hard, as doing so would restrict the flow.

Walk: Monday December 21, location Minnesota River Valley in Chanhassen, Minnesota, altitude 750 to 875 ft (230 to 267 m).  Temperature -14 to -5 F (-26 to -21 C), winds were negligible.  The Insulator was carried in my REI Traverse pack.  I was careful to blow the water out of the hose before departure.  I took my first sip of water about 45 minutes into the hike, and the hose was frozen preventing any flow.


The Insulator reservoir does not freeze up during the day in very cold temperatures inside a backpack.  It can be used to keep water from freezing overnight if topped off with warm water before retiring.  The supply tube can be prevented from freezing for one day by blowing the water back into the reservoir after drinking, but the effectiveness of the tube insulation is questionable.  Once the tube freezes up it is nearly impossible to thaw in the field, as it does not fit into a pot.

I can recommend the system for day hikes where it is unlikely to freeze up, but not for overnight Winter backpacking.  The 3 L (3.2 qt) capacity is more suited for backpacking, so there seems to be a mismatch between the capacity and the use to which it is best suited.

  • The reservoir insulation is very effective at keeping the stored water from freezing at very cold temperatures.
  • The insulation carrying handle is very handy for hanging the reservoir inside a shelter for additional protection.
  • The reservoir can tolerate being filled with hot water, as well as being immersed in boiling water for thawing the contents.
  • By carefully blowing all water out of the supply tube and by drinking frequently I was able to use the Insulator at temperatures above 0 F (-18 C) without supply tube freeze-up during the daytime.
Opportunities for Improvement:
  • The supply tube and bite valve insulation are ineffective.  I was shocked at how quickly it froze, and at temperatures below 0 F (-18 C) I could not prevent the supply tube from immediately freezing.
  • Make it easier to fill the reservoir from another hand-held container.  The reservoir should be able to stand up on its own, and the opening should stay open and not require another hand to hold it open.
  • Make the insulation clasp large enough to operate with gloves on.
  • A more robust bite valve shoulder strap attachment mechanism is needed.  Attaching to the bite valve cap makes the cap susceptible to popping off.
This concludes my Field Report on the Platypus Insulator Hydration System.

Long-Term Report

Field Locations/Conditions

February 12-14, 2009
March 1, 2009, 8AM to noon (dayhike)
March 6-8, 2009
March 28-April 4, 2009
Porcupine Mountains Wilderness, Michigan Upper Peninsula
Afton State Park, Minnesota Eagle Mountain in the Boundary Waters Canoe Area Wilderness (BWCAW) in northern Minnesota
Ozark Trail in south-central Missouri located in the Mark Twain National Forest
778 ft to 1600 ft (237 m to 490 m) 650 ft to 1000 ft (200 m to 300 m)
1700 ft to 2297 ft (520 m to 700 m)
925 ft to 1650 ft (280 m to 500 m)
About 13 miles (21 km) on snowshoes
4.3 miles (6.9 km) on snow without snowshoes
8.8 miles (14.2 km) on snowshoes
91.3 miles (147 km) on foot
Nighttime lows of around 15 F (-9 C), daytime highs of 30 F (-1 C) The morning began around 0 F (-18 C) and climbed to 20 F (-7 C) by noon
Nighttime lows of 15 F to 20 F (-9.4 C to -6.7 C), daytime highs of 25 F (-4 C) to 32 F (0 C).  On March 7 it not only warmed up to about the freezing point, we had strong spring sunshine which had considerable warming power.
Coldest nighttime low was 26 F (-3 C), warmest daytime high was about 70 F (21 C)
Forested with lakes and rivers.  The trail was along an escarpment with some steep grades. Up-and-down topography, climbing out of the St Croix river valley with some serious scrambling.
The first section was on rivers, lakes and creekbeds, then a scrambling steep ascent of Eagle Mountain, followed by a gradual descent on a Forest Service trail.
Heavily forested with oak and hickory.  Many streams, one lake.  Continual climb & descent of Ozark mountains.
Test Result
Froze up the first night
Stayed unfrozen throughout the morning hike
Froze up the first night, but thawed right around noon the next day from exposure to the sun
Removed all insulation before departure.  No freeze-ups of any kind.


When I set out on the Porcupine Mountains trip I was really hopeful that the Insulator was going to be more successful in keeping my water from freezing up than previous outings.  The predicted low temperatures of this trip were supposed to be warmer than the highs of my prior backpacking trips.  Unfortunately, history repeated itself.

On Day One I set out with a full reservoir.  Snowshoeing up the unbroken Escarpment Trail in 3-4 ft (1-1.3 M) of snow was hard work, but the Insulator kept me well-hydrated.  So far, so good.

That evening before retiring I did everything I could to clear the supply hose.  I detached it from the reservoir and sucked all the water out and blew it out until I turned blue in the face.  As far as I could tell there was no remaining water that could freeze.

I was wrong.  The next morning it was frozen up again, and I could not even blow air through the hose.  I put about 1 L (1 qt) of warm water in the reservoir to use in camp that night to melt snow, and filled up my insulated Nalgene for use during the day.

While snowshoe hiking about 6 miles (10 km) that day I struggled to stay hydrated without the use of the Insulator.  I melted snow and replenished my 1 L (1 qt) Nalgene at lunchtime, and rehydrated in the evening as best I could.  Despite my best efforts I was headachy all night long from dehydration.

Once again the Insulator reservoir did a great job of keeping my water from freezing at night by just tossing it into my backpack underneath whatever clothing I kept there at night.

The Afton State Park hike was a training outing conducted by the trip leader of the BWCAW backpack trip the following weekend.  It was intended to assess participant conditioning and gear readiness for the BWCAW.  The morning started out very cold; I was concerned the Insulator would freeze up.  It did not, and I was able to stay hydrated all morning long by sipping from the drinking tube.  Of the six hike participants, I was the only one using a hydration reservoir.  Everyone else relied on insulated Nalgene containers, often struggling to reach their water container.  A 1 L (1 qt) Nalgene barely fits into most backpack water bottle pockets, but when insulated they must be clipped to the side or back of the pack making them impossible to reach.  The other hikers asked someone to reach their water bottle for them or took their packs off, while I smugly sipped from my drinking tube.  Here's a photo of the Insulator at a break during the hike:
Afton state park dayhike
Photo by Martin Kubik

There were four participants in our Eagle Mountain trip to the BWCAW.  The leader was Martin Kubik, legendary Boundary Waters hiker and father of the Kekekabic Trail.  He advised me to "leave the (expletive deleted) reservoir at home" because in his experience reservoirs always freeze up in Minnesota winters, but I wanted to put it to the test and took it anyway.  The result was mixed.  The supply hose froze up on the first night, but actually thawed out in the sunshine on Saturday around noon.  This was handy, as we were just getting ready to ascend Eagle Mountain.  Martin belatedly admitted that the "radiator hose" was actually pretty handy in this kind of terrain, where stopping to take off your backpack to take a drink was difficult.  I was able to stay hydrated easily during the long ascent, where my companions had to work a lot harder to reach their water bottles.  Finally, I felt that my many hours and miles of carrying the Insulator in winter conditions paid off!  Here's a pic of the Insulator on the way up the mountain:
Eagle Mtn
Photo by Martin Kubik

For the Ozark Trail hike weather predictions were for a few sub-freezing nights, but quite warm spring days.  I decided to lighten up and remove bulk by removing all the insulation.  I had no problems with any freezing problems on this trip.


I don't see any way of keeping the Insulator supply hose from blocking with ice up at night in freezing conditions without sleeping with it in my shelter.  I am unwilling to put it inside my sleeping bag for fear that water from it will drain during the night and degrade the insulating properties of my bag.  As a result, I cannot recommend this system for overnight backpacking hydration in freezing conditions unless, as my experience on Eagle Mountain showed, daytime temperatures and sun exposure are such that thawing during the day is possible and acceptable.

I can heartily recommend the system for day hikes in temperatures above 0 F (-18 C).  At these temperatures with a little care in blowing the supply hose water back into the reservoir after every drink, the Platypus Insulator can be an effective piece of gear for all-day hydration.

I appreciated the flexibility of being able to remove all the insulation for warm-weather use.  This allowed me to use the reservoir and supply tube in all types of warmer weather.

See my list of likes and opportunities for improvement in my Field Report for additional summary information.

  • Ability to stay hydrated on an all-day winter hike.
  • No mechanical failures of any kind, particularly no leaks from the seal and fittings.  I've owned several hydration reservoirs that leaked, but I feel I can rely on the Insulator.
Opportunities for improvement:
  • I don't think there's a way to provide enough insulation to prevent the supply tube from freezing at night.  I'd like to see a way to make sure its completely drained in the evening to make this a non-issue.

Many thanks to Cascade Designs Inc. and for the opportunity to test this product.

Read more reviews of Platypus Hydration gear
Read more gear reviews by Kurt Papke

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